1. Field of the Invention
This invention relates to a process for producing immobilized enzyme compositions useful for industrial applications.
2. Description of the Prior Art
Immobilization of enzymes is often very advantageous in industrial applications. One of the industrially important merits is that the immobilized enzymes can be packed in a column type reactor to serve for a continuous enzyme reaction over a long period of time.
Various techniques for the enzyme immobilization have thus far been proposed, particularly with regard to glucose isomerase which, in the immobilized state, has a great importance in industrial applications, for example, in U.S. Pat. No. 3,821,086 to Reynolds (issued June 28, 1975), U.S. patent application Ser. No. 501,292 now U.S. Pat. No. 3,980,521 by NOVO (filed Aug. 28, 1974) and U.S. Pat. No. 3,915,797 to Ishimatsu et al. (issued Oct. 28, 1975).
This invention contemplates to provide a further development over the prior art immobilization techniques, more particularly to provide a process for producing immobilized enzyme compositions of an excellent physical strength, with an outstandingly high enzymatic activity and a resonable stability and showing a sufficient liquid penetration when packed in a reactor of an industrial scale as compared with immobilized enzymes of the prior art.
This invention stems from our prior invention wherein an immobilized enzyme of a high enzymatic activity and an excellent stability can be produced by immobilizing an enzyme and/or enzyme-containing microorganic cells into an anion-exchange high molecular substance containing a quaternary pyridine ring in the molecule, that is, a reactive high polymer insoluble in water but hydrophilic obtained by quaternization of vinylpyridine copolymer, making an improvement in the physical strength of the immobilized enzyme which has been a serious drawback of the above invention.
The above improvement has been attained by the process comprising the steps of subjecting an enzyme and/or enzyme-containing microorganic cells, after reaction with the above described anion-exchange high polymer, to extrusion molding in an extruder under a predetermined humidity condition, pelletizing in a pelletizing machine if required, and then to drying under a certain temperature condition into immobilized enzyme pellets of a 100.mu.-2 mm pellet size. The chemical reaction between the anion-exchange high polymer and the enzyme and/or enzyme-containing microorganic cells can be accelerated by the above drying treatment thus enabling the production of a catalyst of an excellent physical strength. In addition, pelletizing in the extrusion molding prior to the drying can significantly increase the drying efficiency to minimize the heat energy required for the chemical reaction thereby preventing the excess supply of the heat energy which may cause damages to the enzymatic activity.
Besides, a great pressure loss is often experienced with large-scaled industrial reactors or reactors using industrial materials of high density and viscosity such as for the hydrolysis and isomerization of dextrose, and therefore catalysts to be used therein should be strong enough to suppress such a pressure loss. The invention has succeeded in making a further development based on the above improvement by the addition of a bifunctional crosslinking agent capable of reacting with the anion-exchange high polymer or the enzyme described above.
While the above crosslinking agent may be effectively added at any stage of the process, the effect of the addition can be rendered more remarkable by supplying heat energy in the cource of the drying, whereby the physical strength of the catalysts, that is, immobilized enzyme compositions is greatly enhanced, as well as the stability in the enzymatic activity can be improved to produce catalysts of an industrial excellency.
The advantageous features of the excellent immobilized enzyme compositions (catalysts) obtained by the process according to this invention are summarized as follows:
Since the compositions substantially consist of enzymes, highest enzymatic activity can be provided and, in addition, pelletized catalysts of any desired shape and size can be produced by mechanical molding by suitably controlling the molding conditions.
This enables to maintain the reaction at a sufficiently high rate, supplying a material at a high feed rate into a reactor of an industrial scale packed with the enzyme according to the invention. Moreover, since the catalyst is chemically crosslinked and mechanically molded, it possesses a high physical strength and provides an excellent penetration to the liquid passing through the reactor to reduce the pressure losses and to ensure stabilized operation.
In addition, since the mechanical molding and chemical crosslinking improve the chemical stability, there can be obtained various other advantages which were not present in the conventional processes, e.g. less deactivation of the enzyme even during the continuous long use and less effects of the impurities.
Further, the process of this invention is effective not only for the immobilization of an individual enzyme and/or enzyme-containing microorganic cells but also for the immobilization for a plurality of enzyme and/or enzyme-containing cells in combination and therefore provides a wide variety of applications.